Optical time domain reflectometers or OTDRs are used to locate defects in an optical cable by transmitting pulses into the cable and receiving light pulses due to Rayleigh scattering, reflection or other effects. The received light signal is analyzed by correlating time delays between the input signal and the reflected light signals. Certain OTDR systems include displays for presenting loss curves to a user showing trace discontinuities corresponding to defect locations along the length of an optical fiber under test. The design specifications of the OTDR system are related to the speed of light traveling through the cable, the overall length of the cable, and the desired resolution or accuracy of the estimate of the location (distance) of the identified fault(s). It is desirable to provide an analysis with a relatively small resolution in order to facilitate assessment of defects and remedial efforts to repair damaged optical cables. For example, it may be desirable to identify the defect location within a resolution distance of 0.5 m to direct service personnel to the appropriate location for maintenance or repair. However, long cable lengths in combination with relatively small resolution distances leads to analysis of a large sample of data, and the OTDR system must store the sample data in a relatively large electronic memory. Large memories, in turn occupy significant areas on integrated circuits, and consumed power, whereby a need remains for improved OTDR techniques and apparatus for locating defects in an optical cable with relaxed memory requirements.